1. Field of the Invention
The invention is concerned with methods for growing single crystals by flux methods.
2. Description of the Prior Art
Compared with other single crystal garnets such as gadolinium gallium garnet Gd.sub.3 Ga.sub.5 O.sub.12 or gadolinium aluminum garnet, Gd.sub.3 Al.sub.5 O.sub.12, yttrium aluminum garnet Y.sub.3 Al.sub.5 O.sub.12 (YAG), is a preferred laser host medium due to low threshold for lasers utilizing rods of YAG single crystals doped with a trivalent rare earth ion such as Nd.sup.3.sup.+. Since laser rods are typically cut from single crystals, growing large size, high quality single crystals of neodymium doped YAG is commercially significant.
Among techniques for growing single crystals suitable for laser application are the Czochralski pulling technique described, for example, in "Growth of Garnet Laser Crystals", by R. C. Linares in Solid State Communications 2, No. 8, pages 229-231 (1964) and the flux growth technique of primary concern in the following. The growth of YAG crystals from a melt containing Y.sub.2 O.sub.3, Al.sub.2 O.sub.3, PbO, and PbF.sub.2 is described in "Growth of Single Crystals of Yttrium Aluminum Garnet from Lead Oxide-Lead Fluoride Melts", By R. A. Lefever, J. W. Torpy, and A. B. Chase in Journal of Applied Physics, 32, No. 5 pages 962-963, 1961. Flux growth of rare earth doped YAG from a PbO--PbF.sub.2 --B.sub.2 O.sub.3 flux is described in "Growth of Large Optical-Quality Yttrium and Rare Earth Aluminum Garnets", by L. G. Van Uitert, W. H. Grodkiewicz and E. F. Dearborn, in Journal of the American Ceramic Society, Vol. 48, No. 2, pages 105-108, 1965. A detailed description of apparatus facilitating flux growth is given in "Growth of Large Yttrium and Rare-Earth Aluminum and Iron Garnets", by W. H. Grodkiewicz, E. F. Dearborn, and L. G. Van Uitert in Crystal Growth, Supplement, Journal of Physics and Chemistry of Solids, pages 441-444, 1967.
While these references do disclose the feasibility of flux growth of rare earth doped YAG there remains the concern for growing crystals of large size and high quality.